Disk units, such as hard disk drives and DVD drives (Digital Versatile Disk drives), are used for auxiliary information storage devices for personal computers, for example. These disk units have a plurality of power consumption modes and are so constructed that the power consumption mode is changed and controlled on the disk unit side and reduction of power consumption is thereby accomplished.
More specific description will be given. In hard disk drives (hereafter, abbreviated to “HDD”) connected with a personal computer through the AT Attachment (hereafter, abbreviated to “ATA”) interface, for example, power consumption control (power save control) is carried out through the functions described below: Standby Timer function, Advanced Power Management (hereafter, abbreviated to “APM”) function, or the like.
In this case, a plurality of power consumption modes are provided as changeable power consumption modes. Such power consumption modes include, for example, Active mode, Idle mode that is divided into a plurality of stages, Standby mode, and Sleep mode in descending order of power consumption.
The Standby Timer function is for performing the following operation: a time-out value preset by a host device is taken as the initial value; when there is no access from the host device in so-called Idle mode, counting down is started for the time-out value; when the count is zeroed, the mode automatically shifts to Standby mode.
The APM function is for performing the following operation: the HDD itself estimates the pattern of access from the host device to the HDD based on historical information about accessing from the host device; the power consumption mode is changed based on the result of this estimation. In this case, the time taken until the power consumption mode is changed (transition time) is adaptively varied based on the pattern of access from the host device to the HDD.
Various techniques have been disclosed with respect to such power consumption control. For example, Japanese Unexamined Patent Publication No. Hei 9(1997)-6465 discloses the following technique: information processing equipment is provided with a power saving timer, and the value on this power saving timer is adaptively varied. Thus, the power consumption is efficiently reduced without degrading the processing efficiency of the information processing equipment.
More specific description will be given. In the technique described in Japanese Unexamined Patent Publication No. Hei 9(1997)-6465, the following operation is performed: in information processing equipment provided with a power saving timer, the mode is caused to transition to power saving mode when a time set on the power saving timer has passed after the last processing operation. When a task resumption request comes relatively soon after power saving mode is established in this case, the power saving timer is set to a slightly larger value for the next and following operations. Thus, the mode is prevented from unnecessarily transitioning to power saving mode.
If the time from when power saving mode is established to when a task resumption request is made is long, the power saving timer is set to a slightly smaller value for the next and following operations. Thus, the mode is caused to transition to power saving mode as quickly as possible. As mentioned above, Japanese Unexamined Patent Publication No. Hei 9(1997)-6465 describes a technique for estimating the subsequent access patterns from access history and changing the mode as in the above-mentioned APM function of HDDs.
However, the above-mentioned APM function of HDDs and the technique described in Japanese Unexamined Patent Publication No. Hei 9(1997)-6465 have their limit on the accuracy of estimation. This is because, in these function and technique, access patterns are estimated based on the history of access to the device itself that estimates access patterns. For this reason, it is suspected that there are cases where the mode may be caused to transition to a mode with low power consumption; nevertheless, the equipment stands by in high-power consumption mode, such as Active mode, in which much power is consumed.
It is suspected that there are converse cases where it is likely that access immediately takes place; nevertheless, the mode transitions from Active mode, in which operation can be immediately started, to Idle mode or Standby mode, which takes longer time to start as compared with Active mode.
In these cases, wasteful power consumption occurs, and further loss can be produced in processing time by an amount equivalent to the time it takes to transition from Idle mode or Standby mode to Active mode.
Recently, consideration has been given to utilization of hard disk or DVD as a recording medium for so-called mobile devices, such as digital video cameras, which are carried about when used. That is, consideration has been given to mounting a HDD or DVD drive in the enclosure of a mobile device, such as a digital video camera.
In case of mobile device, a battery is used as the power source, and the following requirements must be sufficiently met: lengthening the battery duration, suppressing temperature rise in the enclosure of the mobile device, and the like. However, a problem arises when a HDD or a DVD drive is mounted in a mobile device. These drives are higher in power consumption and produces more heat as compared with the other devices and components mounted in the same enclosure. For this reason, it is desirable that the power consumption should be reliably and sufficiently reduced with respect to various drives, such as HDDs and DVD drives.
The present invention has been made in light of the foregoing. An object of the present invention is to provide an apparatus and a method wherein the power consumption of a disk drive for hard disk and optical disk, for example, can be reliably and sufficiently reduced.